The present invention relates in general to balloon catheters employed in the treatment of vascular diseases. More particularly, the present invention relates to a bifurcated catheter assembly which has two dilation balloons in parallel at the distal end of a single catheter shaft. The bifurcated catheter assembly provides an improved means for treating arterial bifurcations.
In a medical procedure known as percutaneous transluminal coronary angioplasty (PTCA), a balloon catheter is used to treat a coronary artery (or other vessel) which has become narrowed or restricted due to the accumulation of plaque along the artery wall. In the PTCA procedure, a balloon catheter is inserted percutaneously and is advanced through the lumen of the coronary artery to the site of a stenosis. The balloon is then inflated to press the plaque against the artery wall thereby dilating the lumen of the artery and establishing adequate blood flow.
After the PTCA procedure has been performed, a stent (which is well known in the art) may be deployed in the treated area to prevent restenosis and maintain a clear pathway for the flow of blood. A balloon catheter with an expandable stent mounted over the balloon is advanced through the lumen until the stent is in the desired location. The balloon is then temporarily inflated thereby expanding and implanting the stent in the vessel. The balloon is then deflated and the balloon catheter assembly is removed from the lumen, leaving the implanted stent in the vessel to support the vessel wall and prevent development of restenosis.
Although most diseased arteries can be successfully treated in this manner using conventional balloon catheters and stents, arteries which are diseased at a bifurcation are difficult to treat with the devices currently available. For example, when a conventional balloon catheter is used to treat one of the vessel passages at a bifurcation during PTCA, the pressure from the expansion of the balloon in the treated passage can restrict the flow of blood to the untreated passage by pushing the carina over the ostium of the untreated vessel. In addition, the pressure of the balloon in the treated passage may shift the plaque from the treated passage to the untreated passage. If sufficient plaque is shifted to the untreated passage, the ostium of the untreated passage can becomes so occluded that it becomes difficult or impossible to insert a guide wire and catheter to perform a PTCA in the untreated vessel.
Deploying a stent at a bifurcation is also very challenging because the stent must overlay the entire diseased area of the bifurcation, yet not itself compromise blood flow. Conventional stents are designed to repair areas of blood vessels that are removed from bifurcations and, since a conventional stent generally terminates at right angles to its longitudinal axis, the use of conventional stents in the region of a vessel bifurcation may result in blocking blood flow of a side branch (commonly referred to as "jailing" the side branch) or fail to repair the bifurcation to the fullest extent necessary. To be effective, the stent must overlay the entire circumference of the ostium to a diseased portion and extend to a point within and beyond the diseased portion. Where the stent does not overlay the entire circumference of the ostium to the diseased portion, the stent fails to completely repair the bifurcated vessel.
To overcome the problems and limitations associated with the use of conventional stents, a Y-shaped stent has been proposed for the treatment of bifurcations. Such a stent has the advantage of completely repairing the vessel at the bifurcation without obstructing blood flow in other portions of the bifurcation. In addition, such a stent allows access to all portions of the bifurcated vessel should further interventional treatment be necessary. In a situation involving disease in the origin of an angulated aorta-ostial vessel, such a stent would have the advantage of completely repairing the vessel origin without protruding into the aorta or complicating repeat access. The proposed Y-shaped stent provides an improved device for repairing bifurcations, however, the delivery and deployment of such a stent cannot be easily accomplished with a conventional balloon catheter.
Because a conventional balloon catheter is not adequate for treating an arterial bifurcation, many physicians currently employ a "kissing balloons" technique in which two separate balloon catheters are inserted into a guide catheter and each balloon tracks over a separate guide wire. The guide catheter is advanced to a point proximal of the bifurcation site and two guide wires arc then advanced from the distal end of the guide catheter into separate vessel passages. The two balloon catheters then track the guide wires into the respective passages. The balloons are simultaneously inflated using either separate inflation media or from a single source using a manifold which divides the flow. The two catheters are used together for PTCA or stenting so that both vessel passages at a bifurcation site can be treated simultaneously.
Although generally effective, the use of two single balloon catheters to treat arterial bifurcations has significant drawbacks. For example, the presence of two similar catheters exiting the proximal end of the guide catheter makes it difficult for a physician to manage both devices without becoming confused as to which catheter controls which balloon. Furthermore, the presence of two balloon catheters within one guide catheter creates a large device profile thereby limiting the amount of radiopaque dye which can be injected into the vessel to allow the physician to view the bifurcation.
Efforts have been made to develop a balloon catheter which is designed specifically for the treatment of arterial bifurcations. Such efforts have led to the proposal of a Y-shaped balloon disposed at the distal end of a catheter which is inflated in a bifurcation to treat both passages simultaneously. Although a Y-shaped balloon would provide an improvement over the use of two separate balloon catheters, the proposed device may not be practical due to challenges of manufacturing a Y-shaped balloon, attaching it to a catheter shaft, and properly positioning it at a bifurcated blood vessel. A device of this type is described in the international patent application WO 97/16217 dated Oct. 30, 1995 and entitled Angioplasty Device for Arterial Bifurcation.
Thus, there exists a need for an improved balloon catheter which can be used to effectively treat arterial bifurcations both for PTCA and stent delivery and deployment. It is also desirable that such a balloon catheter be easy to use, inexpensive to manufacture, and constructed from materials which are common in the industry today. The present invention addresses this need.